Robert e



INITED STATES PATENT .OFFICE.

ROBERT E. SCHMIDT, OF ELBERE ELD, GERMANY, ASSIGNOR TO THE FARBENFABRIKEN, VORMALS FR. BAYER & CO., OF SAME PLACE.

ALIZARINHEXACYANIN.

SPECIFICATION forming part of Letters Patent No. 506,265, dated October 10, 1893. Application filed May 11, 1892. Serial No. 432,611. ($pecimens.) Patented in England March 12,1892, N0- 4,8'71.

To all whom, it may concern:

Be it known that I, ROBERT E. SCHMIDT, doctor of philosophy and chemist, (assignor to the FARBENFABRIKEN, VORMALS FR. BAYER & 00., of Elberfeld,) a subject of theEmperor of Germany, residing'at Elberfeld, Germany, have. invented a new and useful Improvement in the Manufacture of Alizarin Derivatives, (for which the aforesaid FARBENFABRIKEN have already obtained Letters Patent in England, No. 4,871, dated March 12, 1892,) of which the following is a clear and exact description.

I have described in the United States Letters Patent No. 446,893, dated February 24, 1891, the production of an alizarin derivative called alizarin bordeaux which I haveobtained by oxidizing alizarin with a large excess of sulfuric anhydride in the form of a strong fuming sulfuric acid at a low temperature.

In the United States Letters Patent No. 446,892, dated February 24, 1891, I have described another valuable alizarin dye-stuff which is produced by oxidizing the aforesaid alizarin bordeaux in sulfuric acid solution with manganese dioxid. While the alizarin bordeaux is a tetraoxyanthraquin'one the product resulting from alizarin bordeaux by further oxidation represents a pentaoxyanthraquinone. In order to express the constitution and the cyanine like character of this latter product I briefly term it alizarin pentacyanin.

My new invention relates to the production of a new coloring-matter byfurther oxidizing the said alizarin pentacyaniu a dye-stud being thus formed which is a hexaoxyanthraquinone and which I briefly term alizarin hexacyanin. It is difierent from the alizarin pentacyanin by its composition and properties, from the isomeric hexaoxyanthraquinone which I have described and claimed in a separate application and which I briefly term hexaoxyanthraquinone it chiefly differs by its dyeing properties. The production of this new coloring-matter called alizarin hexacyanin may be carried out in the following different ways; first, by oxidizing alizarin pentacyanin or alizarin bordeaux in sulfuric acid solution with manganese dioxid, arsenic acid or other suitable oxidizing agents; secondly, by heating alizarin pentacyan'in with concentrated sulfuric acid at higher temperapurin (tetraoxyanthraquinone) which corre-' sponds with anthrapurpurin in a like manner as purpurin does with alizarin, is totally changed into alizarin hexacyanin by the further action of the oxidizing agents employed.

In carrying out the preceding three processes practically I proceed as follows: Ten

parts,-by weight, of dry alizarin pentacyanin' are dissolved in two hundred parts, by weight, of concentrated sulfuric acid of'66 Baum and five parts, by weight, of finely pulverized manganese dioxid containing ninety per cent. of dioxid, are gradually added. In the first place the quinone of alizarin pentacyanin, a so called anthradiquinone, is formed which may be recognized when a portion of the resulting mixture, dissolved in concentrated sulfuric acid, shows no more distinct absorption bands when looked at in the spec'- troscope. The quinone of alizarin pentacyanin, then, is converted into the quinone of alizarin hexacyanin by the further action of the manganese dioxid, employing advantageously a somewhat higher temperature. Therefore it is most practical to heat the mixture under continual stirring at a temperature of about centigrade until a test portion after pouring into water and boiling with acid sodium sulfite forms a precipitate the solution of which in concentrated sulfuric acid shows no more the absorption bands of alizarin pentacyanin. The resulting mixture then is poured intotwo thousand parts, by weight, of water: adding ten parts, by weight, of an aqueous acid sodium sulfite solution of 34 Baum. After heating to the boiling point the coloring-matter separating is filtered off and washed out. The latter is redissolved in the necessary quantity of soda-lye and the alkaline solution after having been filtered is decomposed by the addition of acids. The product precipitated is a mixture of alizarin hexacyanin and hexaoxyanthraquinone, as above mentioned. In order to remove the latter, the mixture is crystallized at first out of nitrobenzene, then repeatedly out of alco- 1101, in which the hexaoxyanthraquinone is more difficultly soluble than alizarin hexacyanin. A second and best method of separating the two coloring-matters of the above mixture is to be carried out by heating the mixture with sodium acetate and acetic acid anhydrid and boiling the resulting mixture of the two isomeric hexa-acetyl-compounds with acetone by which the hexa-acetyl derivative of hexaoxyanthraquinone is not dissolved while that of alizarin hexacyanin easily dissolves in the said solvent. By saponi fying the acetyl compounds thus separated the alizarin hexacyanin and hexaoxyanthraquinone are obtained in a pure state.

As alizarin pentacyanin is produced by oxidizing alizarin bordeaux, it is not necessary to start from alizarin pentacyanin but alizarin bordeaux may be employed without isolating the alizarin pentacyanin produced as an intermediate product.

The following is an example for the con version of alizarin bordeaux into alizarin hex acyanin: Ten parts, by weight, of dry alizarin bordeaux are dissolved in two hundred parts, by weight, of concentrated sulfuric acid at 66 Baum and fifteen parts, by weight, of finely pulverized manganese dioxid (containing ninety per cent. of dioxid) are gradually introduced, the temperature being kept at from 50 to 55 centigrade. The gradual conversion of alizarin bordeaux into alizarin pentacyanin and alizarin hexacyanin isto be recognized very distinctly by the usual spectroscopic examination. When the spectrum of the pentacyanin has totally disappeared the sulfuric acid liquid is treated in the same manner as described in the preceding example.

111 order to oxidize alizarin bordeaux in sulfuric acid solution by means of arsenic acid a higher temperature for example from to centigrade is necessary. The alizarin pentacyanin formed at first in this operation seems to be immediately converted into alizarin hexacyanin and hexaoxyanthraquinone, as in the spectroscopic examination of the oxidation products the alizarin pentacyanin is always to be recognized only in very small traces.

The following may be given as an example for the preparation of alizarin hexacyanin by oxidizing alizarin bordeaux by means of arsenic acid: A mixture of ten parts, by weight, of alizarin bordeaux, two hundred parts, by weight, of sulfuric acid at 66 Baum and fifteen parts, by weight, of dry arsenic acid are heated for about six hours at a temperature from 140 to 150 centigrade and the resulting mixture then is poured into water. By filtering off, redissolving in alkali and precipitating again with acids, separating the two products formed in the manner before described the alizarin hexacyanin dye-stuif is isolated.

Of course, on starting from alizarin pentacyanin in the last example a smaller quantity of arsenic acid is necessary for effecting the oxidation of alizarin pentacyanin into alizarin hexacyanin. At the high temperature employed in this example as well as in the following quinones are not formed as I have found the mixture contains the coloring matters and not the quinones thereof.

In order to produce alizarin hexacyanin by treating alizarin pentacyanin with concentrated sulfuric acid at higher temperatures I proceed as follows: Ten parts, by weight, of alizarin pentacyanin and two hundred parts, by weight, of sulfuric acid at 66 Baum are heated at centigrade until a sample of the mixture diluted with sulfuric acid shows no more the spectrum of alizarin pentacyanin. When the latter has been found to be totally converted the whole liquid is poured into water and the coloring matter separated by fil tering off, washing out and isolated in the manner above described.

Anthrapurpurin is converted into pure alizarin hexacyanin by an energetic oxidation with the aid of manganese dioxid. In the first place there is formed oxyanthrapurpurin which is a coloring-matter dyeing a yellowishred on cotton mordanted with alumina salts, but possesses only an inferior value for dyeing purposes. By the further oxidation the oxyanthrapurpurin is transformed into the quinone of alizarin hexacyanin and this quinone, is then converted into the cyanin (alizarin hexacyanin) by a subsequent treatment with reducing agents employing most practically sulfurous acid. The following example may illustrate how this operation is to be carried out: A pulverized mixture containing ten parts, by weight, of anthrapurpurin and nineteen parts, by weight, of manganese dioxid (ninety per cent.) is introduced with constant agitation into three hundred parts, by weight, of sulfuric acid at 66 Baum taking care that the temperature does not rise above 35 centigrade. After the whole manganese dioxid has been added, the mixture is allowed to stand for half an hour. Then it is poured into three thousand parts, by weight, of water mixed with ten parts, by weight, of an aqueous solution of sodium bisul fit at 55 Baum. The liquid is heated to the boiling point and the coloringinatter separated is filtered off, washed out and purified by redissolving, dad, in the well known manner.

I have further found that in general in order to Separate pure alizarin hexacyanin from other oxyanthraquinones especially in case the former be in excess the best method is the following: The mixture is dissolved in twenty times its weight of concentrated sulfuric acid and after heating to 100 centigrade water is gradually added to the cooled solution. In this manner the hexacyanine is precipitated at first and in a pure state as the other oxyanthraquinones, remain dissolved in the diluted sulfuric acid solution. The alizarin hexacyanin can readily be isolated by filtration.

My new product thus obtained and called alizarin hexacyanin is insoluble in water and very moderately soluble in alcohol with dark rose-red color and in glacial acetic acid with a more yellowish-red color both solutions showing a yellowish-bro wn fluorescence. Out of alcohol or glacial acetic acid it separates in dark brilliant crystals. It is easily soluble in boiling nitrobenzene and very easily in pyridin. Whenits alkaline solutions are decomposed by adding acids or on pouring its solution in concentrated sulfuric acid into water it separates in reddish-brown flakes which after filtering off yield a dark brown paste that is most fit for dyeing and printing purposes. It dissolves in sodium carbonate with bluish-violet color, in ammonia at first with dull brownish-violet color which gradually changesinto a pure and beautiful blue when the solution is allowed to stand in open vessels. By soda-lye it is dissolved with greenish-blue color and out of this solution when in contact with the atmospheric air dark violet flakes separate which I have found are the sodium salt of the quinone of alizarin hexaoyanin. Its solution in concentrated sulfuric acid possesses a bluish color and shows when looked at with the spectroscope two characteristic absorption bands namely: the one in the red part and the other between the yellow and green part of the spectrum. This sulfuric solution, however, assumes a color more greenish when it is allowed to stand for a longer time and thenthe hexaoxyanthraquinone described by mein a separate specification by the following properties: Alizarin hexacyanin dissolves in a solution of sodium carbonate with bluishviolet,.in soda-lye with greenish-blue color, dark violet flakes being separated out of such solution in soda-lye after some time in the air, in ammonia with dull brownish-violet color,

which changes into blue in the air, and in pure concentrated sulfuric acid with .blue color which turns green by standing and. on, adding water to such sulfuric acid solutionat first into violet, then into red, brownish-red. flakes being separated after some time. Hexaoxyanthraquinone. dissolves in a solution of. sodium carbonate with bluish-red, in sodalye with violet color which gradually turns into blue in the air blue flakes being further separated after some time, in ammonia liquid with bluish-red color which changes into violet in the air, in pure concentrated sulfuric acid with bluish-violet color which turns into yellowish-red on adding water, yellowish-brown flakes being separated after some time. The said alizarin derivatives further differ by the absorption spectra of their sulfuric acid solutions. Alizarin hexacyanin displays two strong absorption bands, the one in the red part and the other in the green part of the spectrum, while hexaoxyanthraquinone shows one strong absorption bandin the orange part and a slighter one in the yellowish-green part of the spectrum.

The shades produced by alizarin hexacyanin on wool mordanted with chromium or alumina salts are in general more greenish than those obtained by employing hexaoxyanthraquinone. It produces on wool mor-' danted with alumina salts violet, on W001 mordanted with chromium salts blue shades both being more greenish than those resulting from the alizarin pentacyanin and hexaoxyanthraquinone which I have described in separate specifications.

By analyzing the crystalized productl have found it to be a hexaoxyanthraquinone of the formula (J ,H,O (OH) isomeric with the hexaoxyanthraquinone obtained by me and described in a separate specification, Serial No; 412,304, filed November 18, 1891;

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

1. The process of producing a new alizarin dye stuff by oxidizing alizarin pentacyanin or alizarin bordeaux, substantially as described.

2. The new dye herein described,insoluble in water, moderately soluble in alcohol and glacial acetic acid with yellowish-brown fluorescence, crystallizing from these solvents in dark brilliant crystals; easily soluble in boiling nitro benzol, and in pyridin; soluble in aqueous ammonia with a dull brownish color, which changes on exposure to air to a pure blue; soluble in alkali carbonates and caustic alkalies, from which solutions acids precipi-v tate the dye stud in. reddish-brown flakes, which,after filtering and washing, are a very suitable paste for use in the arts, producing IIO red and one between the yellow and green In testimony whereof I have signed my part of the spectrum, and assumes a more name in the presence of two subscribing witgreenish color 011 standing for a long time, at nesses.

the same time enlarging the absorption band ROBERT E. SCHMIDT. 5 in the red and diminishing the one between Witnesses:

the yellow and green part of the spectrum, XVM. ESSENWEIN,

having the qualities substantially as set forth. RUDOLPH FRIEKE. 

